Friday, April 15, 2005, 16:00
WHGA Auditorium
E. Pedroni, PSI
Abstract:
The rationale of using proton therapy is to deliver a
highly conformal dose to the target volume, while keeping the dose burden to
the surrounding healthy tissues lower by a factor 2-5 compared to conventional
radiotherapy with photons, using technologies which were originally developed
for basic research in medium energy physics. The only real disadvantage of this
approach is the size of the bulky equipment needed for the acceleration and the
transport of the proton beam. PSI has
played and will continue to play a leading role in the technological
development of this field. PSI is still the only place in the world where proton
therapy is applied with a dynamic beam delivery technique, the so-called spot
scanning technique. The PSI gantry is also the most compact system of its kind.
With the availability of hospital-based facilities delivered by industry,
proton therapy is now rapidly diffusing in large hospitals, mainly in the USA
and Japan (but China, Korea and Europe are following). Most of the newly
realized hospital facilities are trying to implement a spot scanning technique
into their basic equipment in addition to the more traditional method of using
passive scattering. Based on the successes of the last ten years, the PSI
directorate decided in 2000 to expand the existing proton therapy activities
and launched the so-called project PROSCAN. This project consists of the
installation of a dedicated superconducting cyclotron for serving the existing
Gantry 1, a second generation gantry (Gantry 2) and the transfer of the eye
treatments (OPTIS2) to the new medical complex. The availability of a dedicated
accelerator in combination with a new gantry will offer us new opportunities to
further improve our pencil beam scanning technology. The idea is to be able to
deliver the dose with repainting, by increasing the speed of scanning by at a
least a factor of ten compared to Gantry 1. The new items used on Gantry 2 for
speeding up scanning are: - the double parallel magnetic scanning of the beam
of Gantry 2, - fast dynamic changes of the beam energy and the shaping of the
dose through the modulation of the beam intensity at the ion source as an
active component of scanning. This should allow to treat on Gantry 2 all
patient body regions, including moving targets. Targets with big motion will be
treated in connection with gating (synchronization with the respiration cycle)
or by steering the beam to follow the target motion (tracking). The goal is to
realize a generalized beam delivery method based on scanning capable of
treating any part of the body.